WASHINGTON — The U.S. Food and Drug Administration here is conducting genetic tests to establish a possible link between consumer illnesses and samples of pistachios containing multiple strains of Salmonella.

Earlier this week, Setton Pistachio, Terra Bella, Calif., issued a voluntary recall of specific lots of approximately 1 million pounds of bulk roasted in-shell and roasted shelled pistachios that were shipped on or after Sept. 1, 2008.

The FDA first learned of the problem on March 24, when it was told by Kraft Foods that its Back to Nature Trail Mix was found to be contaminated with Salmonella. Kraft was initially alerted by its supplier, Georgia Nut Co., that tests conducted by Georgia Nut revealed the potential for Salmonella contamination in pistachios that it sourced from Setton Pistachio. Kraft subsequently sent its auditors to Setton, and identified the source of contamination to be pistachios there.

Since the nuts were used as ingredients in a variety of foods, additional pistachio product may be recalled, according to the FDA.

So far Kroger’s Private Selection Shelled Pistachios and Kraft's Planters and Back to Nature products containing pistachio nuts have been pulled from shelves.

Several illnesses have been reported by consumers that may be associated with the nuts, but it’s not yet known whether any of the Salmonella strains found in the pistachio products are linked to an outbreak.